The present invention relates to a sputter profile simulation method for simulating the profile of a film formed on a semiconductor substrate during the sputtering process of the semiconductor device manufacturing process.
An example of a conventional sputtering profile simulation method is disclosed in Japanese Patent Publication (unexamined) No. A-10-015101 and is described in xe2x80x9cA Practical Sputter Equipment Simulation System for Aluminum Including Surface Diffusion Modelxe2x80x9d by H. Yamada, pages 77-78 in xe2x80x9cSISPAD96 Technical Digestxe2x80x9d issued from Japan Applied Physics Society.
This simulation method comprises means for directing a flux to the profile, means for judging whether or not the flux is shadowed, and means for moving the profile point when the flux is not shadowed.
The conventional sputter profile simulation system with this configuration operates as follows. That is, the following quasi-three-dimensional shadow judgment is made from the sputter particle trajectory to calculate the film growth. First, {circle around (1)} create string data connecting the coordinates of the outline obtained as the cross section of the contact hole along the center line to generate a model of the contact hole profile, {circle around (2)} select one of the coordinates forming the profile at which film growth is to be calculated and direct the sputter particle trajectory calculated by the Monte Carlo method toward that point, {circle around (3)} select one of profile points for shadow judgment and calculate the distance between this point and the contact hole symmetrical axis, {circle around (4)} calculate the intersection of the horizontal plane containing profile points for shadow judgment and the trajectory and, if the distance between the intersection and the contact hole symmetrical axis is larger than the distance between the profile point for shadow judgment and the contact hole symmetrical axis, determine that the particles will not be supplied through shadow effects, {circle around (5)} move the coordinates for film growth calculation into the direction of trajectory if no shadow effect is generated, {circle around (6)} make a shadow judgment for all profile points according to steps to {circle around (3)} to {circle around (5)}, {circle around (7)} calculate film growth at all profile points according to step {circle around (2)} to {circle around (6)}.
The problem with this conventional technique is that the shadow judgment to determine whether or not sputter particles will contribute to film growth takes long calculation time. This is because the shadow judgment is made for all sputter particles including those which will not contribute to the growth of a film of sputter particles. In addition to the patent publication described above, earlier patent disclosures dealing with profile simulation are found in Japanese Patent Publication (unexamined) No. A-6-52269, Japanese Patent Publication (unexamined) No. A-8-171549, and Japanese Patent Publication (unexamined) No. A-8-274084. Japanese Patent Publication (unexamined) No. A-6-52269 discloses a three-dimensional shadowing effect calculation method in which a mesh is defined for the surface of an object and a set of hidden mesh points are identified from the profile of the neighboring areas. Japanese Patent Publication (unexamined) No. A-8-171549 and Japanese Patent Publication (unexamined) No. A-8-274084, applied by the same applicant, disclose a prior art of profile simulation. These known techniques also take long calculation time in simulation.
In view of the foregoing, it is an object of the present invention to provide a sputter profile simulation method which reduces the calculation time. The method is a computerized simulation method comprising the steps of calculating sputter trajectories of particles emitted from a sputter target; projecting the sputter trajectories onto one or more first planes; extracting an outline of a contact hole on a second plane parallel to one of the first planes; defining two shadow points preventing the particles from going to a film-growth calculation coordinates point; and judging that, out of the sputter particle trajectories projected on the first plane, the sputter trajectories between two lines as film-growth contributing trajectories, the two lines joining the film-growth calculation coordinates point to each of the two shadow points.
Sputter trajectory calculation is made, for example, by the Monte Carlo method. The sputter trajectories may be projected on one plane only. For higher efficiency, a plane parallel to the cross section of the contact hole is usually used. In the embodiments, two planes, the XZ plane and YZ plane in the XYZ coordinate system, are used. The shadow point should be a point such that the line starting at the film growth coordinates inside the contact hole is tangent to the innermost point of the contact hole outline. Note that there is no need for three-dimensional film growth processing for all sputter trajectories. Those sputter trajectories not contributing to film growth are eliminated beforehand. That is, based on the relation between the sputter trajectory projection onto the plane and the contact hole outline on a plane parallel to the projection plane, the sputter trajectories which generate shadows and do not reach the film growth coordinates inside the contact hole are eliminated. After that, a three-dimensional judgment is made according to the required precision to calculate the film growth. Thus, instead of calculating the film growth for all sputter trajectories, this method performs simulation more quickly.